fooferdoggie 

I had about 6000 miles in a year on my rear wheel and I had some wobble I the rim it made my bike shimmy. took it to my close high end shop and they had trouble getting spoke tension balanced and said the wheel was going to be problematic. it is a cheap wheel that came with the bike a Shimano deore hub 12 gauge straight spokes and the rim has ss eyelets but I guess that did not help. when I got that info I planned on buying a new rear wheel for my birthday. a dt Swiss hub so I can change it over if needed to a through axle later Sapim triple butted spokes and a dt Swiss rim. I found a shop that all the do is build wheels and hopefully I will have the new wheel next week. the guy looked at my wheel and found the cracked rim. I will take it to my shop and see if the rim will get replaced under warranty. I guess bulls does not warranty wheels so all the parts have their own warranties.
I wewight 200 carry groceries all the time and this is my commuter mid drive bike so it is 70 pounds I put about 6000 miles a year on the bike.

Andrew R Stewart 

Rim spoke hole cracking is a well known cause of rims to need replacing. Fatigue over the miles is the cause. High spoke tensions, too weak a rim's poke bed, peak loads, number of cycles of stress (wheel rotations AND pedal strokes) all combine to result in this.

12 spokes?? Or the spoke gage is 12? If the spoke gage is really 12g then that is also a contributor to rim cracking as the spokes have less elasticity. Rigid spokes pass more peak stress to the rim. BTW I didn't know that Shimano ever made a Deore hub suitable for 12g spokes.

SS eyelets are not visible to my eyes. Must be what are called "internal" eyelets which Mavic has used on some rims. I do see what looks to be corrosion about the spoke hole )and I should have added this to the above causes list).

The solution is a simple one. Replace the rim. Of course a good shop will likely not want to reuse the spokes so they get replaced too most often (even if they are the correct length for the new rim). Then there's the question of the hub's condition. This should be discovered before any new rim is laced up. Often one will find a prebuilt wheel is far less expensive then a custom wheel with new spokes and rim will cost. Of course the prebuilt wheel is price point based and that custom wheel lets one choose butted spokes of greater numbers (36) and generally have better tension levels that a prebuilt one will. Andy

trailangel

Most likely you have exceeded the Weight limit for the wheels. You don't say what brand they are?

fooferdoggie 

oops should have been 14 gauge straight spokes. I was thinking of my first e bike with 12 gauge broke 3 spokes in 600 miles.
I am below the weight limit on the bike but I ride a lot and at 20+ mph on sometimes rough pavement the wheels get a workout. the rim is a Ryde Taurus 2000 the wheel has about 9000 miles on it right now.
I could not find anything in stock its hard right now. but it is only 380 for a really well built wheel that will be worry free and may move on to a another bike. plus a easy to service hub will be nice. the wheel had stayed pretty true when it got a slight tuneup at about 6000 miles. then maybe in the last several hundred got a wobble in the rim you could feel. I thought it was just a uneven pannier load. thew mechanic had a tough time with the wheel spoke tension and told me the wheel was going to be an issue. maybe it did not have cracks then or he would have noticed. I thin kI put maybe 400 or so miles on it when the wheel builder saw the cracks. it was a pretty trouble free wheel though but in the last few weeks my level of power I could put out went up and maybe that was too much for the wheel.

Andrew R Stewart 

No wheel is worry free. Well built wheels are less worry prone though.

I mentioned peak loads and cycles of them. I suspect these are the biggie factors here. A rider's power has little to do with peak loads as strong riders can pedal real smooth and a weak rider can pedal squares. Plus that strong rider might be better at avoiding road surface crap and the weak rider might not get off the seat when it counts and/or be oblivious to the potholes and such. It's the rider that controls the vast majority of the reasons why wheels see a hard life and become problematic. Andy

Amt0571

Well, there are also some wheels that are simply crap. On my old mountain bike I cracked two identical rear rims like the OP in 3 years. They were cheap Rigida rims that came with the bike.

I replaced them with Fulcrum wheels and, despite having 8 spokes less, I had 7 years of trouble free riding until I finally sold the bike.

fooferdoggie 

I think the bike was rated at 230 or 250 cant remember and I doubt I exceeded that. ham pretty careful riding but sometimes it gets a little rough when it is raining and sometimes raining in the dark but no real hard wacks. I will see what the shop sacsabout the rim Tuesday. but if I am going to replace it might as well get a much better wheel its not that much more and tt will be built for my use.

Koyote

Andrew, I once had a rear wheel with too little spoke tension, and that rim developed the same cracks. Is that a potential cause, or was it just coincidence?

Andrew R Stewart 

Generally too little spoke tension will be a spoke breakage potential issue. But as mentioned there's other aspects at play and not yet mentioned by you so...

Spoke tension can change over the wheel's life so that's a moving contribution sometimes. Andy

fooferdoggie 

well got the new wheel today almost did not get it for another week as they shipped the wrong hole rim but he found one locally and grabbed it this morning. wrote 14 miles to grab it wrote to my shop and changed over. went from 6 bolt rotor to center lock so much easier to deal with. but this is a tubeless ready rim and its harder to get there tire on and I killed the tube then I learned its harder to get the tire off. so got that fixed then I had to adjust the brake caliper since it was setup for the 6 bolt. so took off for home to only get a error on the bike computer. I forgot to put the magnet back on the spoke. had to go back and put it on.
the rear feels far more solid now no more shimmy I was feeling. I got a dt sows hub and rim with sipam triple butted spokes. Will get a front wheel too but they wont have the rim in till next week. but I was only worried about the back.
I was not sh=ure hwo to carry the wheel then I realized how and brought zip ties worked well. then had to wait for a long slow train.